ANTENNA HAVING A WAVEGUIDE STRUCTURE AND METHOD OF ITS MANUFACTURE

Abstract

 An antenna having a waveguide structure and comprising a base of a thin flat metal; a radiation plate of a thin flat metal arranged in parallel with the base at a distance from the base; and a plurality of thin flat metal side walls secured to the base and radiation plate, and arranged in the space between the base and the radiation plate so as to form a plurality of waveguides connected to each other. The radiation plate and the side walls are joined by spot-welding at given intervals. The base and the side walls are preferably in the form of a single block made of a metallic material.

Description

TECHNICAL FIELD

[0001] The present invention relates to an antenna of a waveguide structure and a method of manufacturing the same, and more particularly to an antenna of a leaky waveguide structure and a method of manufacturing the same.

BACKGROUND ART

[0002] An antenna of a waveguide structure is generally known as an example of an antenna used for receiving satellite broadcasting. This antenna is provided with a radiation plate, in which slots are formed at predetermined intervals for performing transmission-reception of electromagnetic waves in a band having a central frequency of 11.85 GHz efficiently, and a plurality of parallel waveguides provided under the radiation plate for transmitting the electromagnetic waves.

[0003] An antenna of a leaky waveguide structure that is a sort of the antenna described above is constructed of a main body and a radiation plate made of a metal such as aluminum or copper. The main body includes one flat bottom plate and a plurality of elongated rectangular sidewalls fixed perpendicularly to the bottom plate. The radiation plate is made of a flat plate and arranged in parallel to the bottom plate with a given distance therebetween so as to provide a space between one surface of the bottom plate and one surface of the radiation plate. The plurality of sidewalls serve as partitions for separating the space into one elongated feed waveguide and a plurality of parallel radiation waveguides, each conducting at its one end with the feed waveguide. Thus, one side in a longitudinal direction of each sidewall is fixed to the one surface of the bottom plate, and an opposite side thereof is fixed to the one surface of the radiation plate so that the one feed waveguide and the plurality of radiation waveguides separated by the sidewalls are formed in the space between the bottom plate and the radiation plate. Further, a plurality of slots are formed at a part of the surface of the radiation plate facing to each radiation waveguide. An antenna of a leaky waveguide structure constructed as mentioned-above is described in, for example, the following documents.

(1) Furukawa et al.: "Beam-Tilt Planar Waveguide Slot Antenna of Single Layer Structure for Satellite TV", The Institute of Electronics and Information Communication Engineers in Japan, AP88-40. July 1988.

(2) Hirokawa et al.: "Design of a Crossed Slot Array Antenna on a Leaky Waveguide", The Institute of Electronics and Information Communication Engineers in Japan, AP92-37. May 1992.

(3) Kiyohara et al.: "An Analysis and a Design of Cross Slots for a Leaky-wave Antenna", The Institute of Electronics and Information Communication Engineers in Japan AP91-75. September 1991.

(4) Hirokawa et al.: "Single-Layer Slotted Leaky Waveguide Array for Mobile DBS Reception", Technical Report of IEICE AP93-25, SAT 93-8. 1993-05.

(5) Japanese Patent Application No. 5-276152 (U.S. Patent Application No. 08/169/215, Canada Patent Application No. 2,111,394, Korea Patent Application No. 24577.93 and Taiwan Patent Application No. 82109579 correspond thereto, respectively.)

[0004] In an antenna of a conventional waveguide structure, the radiation plate and the waveguides have been connected to each other by fixing the radiation plate to the sidewalls of the waveguides by screws. Riveting and caulking may be used as another means for connecting the radiation plate with the waveguides. In these conventional methods, however, production steps are increased. Further, each sidewall has to be made thicker sufficiently to provide a space for screw clamping or riveting and to prevent distortion caused by clamping force thereof. Similarly, the radiation plate has also to be made thicker for security of the strength in screw clamping or the like and prevention of distortion. For reason of the foregoing, the antenna becomes expensive and the weight thereof is increased. As a result, it becomes difficult to obtain desired performance of the antenna. Furthermore, excessive thickness of the sidewalls and the radiation plate causes the necessary power of a driving control portion to increase and makes miniaturization of the device difficult when the antenna is used as a mobile antenna with a tracking mechanism or the like. Further, the distortion incurs lowering of transmission efficiency of the waveguide.

DISCLOSURE OF INVENTION

[0005] It is an object of the present invention to provide an antenna of a waveguide structure that is light in weight and has less distortion and simple in its manufacturing method and a method of manufacturing the same.

[0006] According to one aspect of the present invention, an antenna of a waveguide structure includes a flat thin metallic bottom plate; a flat thin metallic radiation plate arranged in parallel to the bottom plate with a certain interval from the bottom plate so as to provide a space between the bottom plate and the radiation plate; and a plurality of flat and thin metallic sidewalls disposed in the space and fixed to the bottom plate and the radiation plate so as to separate the space between the bottom plate and the radiation plate into a plurality of waveguides conducting with one another; wherein the radiation plate is joined to the plurality of sidewalls by a plurality of spot welds at predetermined intervals.

[0007] According to another aspect of the present invention, an antenna of a waveguide structure includes a flat thin metallic bottom plate; a flat thin metallic radiation plate arranged in parallel to the bottom plate with an interval from the bottom plate so as to provide a space between the bottom plate and the radiation plate; and a plurality of flat and thin metallic sidewalls disposed in the space and fixed to the bottom plate and the radiation plate so as to separate the space between the bottom plate and the radiation plate into a plurality of waveguides conducting with one another; wherein the plurality of sidewalls are formed into a single block of metallic material integrally with the bottom plate.

[0008] According to one aspect of the present invention, a method of manufacturing an antenna of a waveguide structure, which includes a flat thin metallic bottom plate; a flat thin metallic radiation plate arranged in parallel to the bottom plate with an interval from the bottom plate so as to provide a space between the bottom plate and the radiation plate; and a plurality of flat and thin metallic sidewalls arranged in the space and fixed to the bottom plate and the radiation plate so as to separate the space between the bottom plate and the radiation plate into a plurality of waveguides conducting with one another, includes the step of joining the radiation plate to each of the plurality of sidewalls by laser welding.

[0009] According to another aspect of the present invention, a method of manufacturing an antenna of a waveguide structure, which includes a flat thin metallic bottom plate; a flat thin metallic radiation plate arranged in parallel to the bottom plate with a certain interval from the bottom plate so as to provide a space between the bottom plate and the radiation plate; and a plurality of flat and thin metallic sidewalls disposed in the space and fixed to the bottom plate and the radiation plate so as to separate the space between the bottom plate and the radiation plate into a plurality of waveguides conducting with one another, includes the step of forming the bottom plate and the plurality of sidewalls fixed to the bottom plate in a form of a single block of metallic material.

[0010] Aluminum, copper or the like is used as the material of a main body including the bottom plate and a plurality of sidewalls and that of the radiation plate. In particular, aluminum is preferred in its workability and electrical characteristics. Further, it is desired to plate an inner surface of the waveguide with gold or silver in order to increase the transmission efficiency. A solid-state laser such as YAG laser and ruby laser is suitable for laser welding. Spot welding performed at a predetermined pitch is desired for laser welding. In this case, it is desired to set the pitch of the spot welding to 1/10 or less of the wavelength of the used electromagnetic wave (2.6 mm or less in the case of 11.85 GHz). This is because the substantially same effect as that obtained in continuous welding can be obtained.

[0011] Further, the main body is preferably produced by casting. When the main body is produced by casting, it is possible to make the main body highly in precise at a low price. A die casting method, a lost wax method, a shell mold method or the like is suitable as the casting method. When the laser welding is performed from the top surface of the radiation plate, welding workability is excellent. When the laser welding is performed while forming a conical dent in advance at each welding position by punching or the like, it is possible to save the necessary power of laser and also to prevent excessive welding metal from swelling on a radiation surface. The maximum diameter and the depth of the dent are suitably about 1/3 to 1/2 and 1/4 to 1/2 of the thickness of the radiation plate, respectively.

[0012] Since the heat is concentrated on a very small point in laser welding, it is possible to fix the main body to the radiation plate by a small amount of weld metal, and distortion caused by welding becomes less. Therefore, it is possible to make the sidewalls and the radiation plate thinner.

BRIEF DESCRIPTION OF DRAWINGS

[0013] 

Fig. 1 is a perspective view showing an external appearance of an antenna of a leaky waveguide structure according to one embodiment of the present invention;

Fig. 2 is a perspective view showing a structure of a main body of the antenna of a leaky waveguide structure shown in Fig. 1;

Fig. 3 is a sectional view taken along a line III-III in Fig. 1;

Fig. 4 is an enlarged sectional view showing an example of a spot weld between a radiation plate and a sidewall;

Fig. 5 is an enlarged sectional view showing another example of a spot weld between a radiation plate and a sidewall;

Fig. 6 is a perspective view showing an external appearance of an antenna of a leaky waveguide structure according to another embodiment of the present invention; and

Fig. 7 is a perspective view showing the structure of the main body of the antenna of a leaky waveguide structure shown in Fig. 6.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] An embodiment of the present invention will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a perspective view showing an exterior configuration of an antenna of a leaky waveguide structure according to an embodiment of the present invention. The external appearance of an antenna of a waveguide structure according to the present invention is not different basically from a conventional unit. Namely, an antenna 1 of a waveguide structure is manufactured with a main body 2 and a radiation plate 5 made of a metallic material such as aluminum or copper. As shown in Fig. 1 and Fig. 3 showing a section taken along a line III-III in Fig. 1, the main body 2 includes a flat bottom plate 3 and a plurality of sidewalls 4A, 4B and 4C each being formed of a substantially rectangular elongated thin plate. The bottom plate 3 and the sidewalls 4A, 4B and 4C are made of aluminum integrally in one block by casting, e.g. by a die casting method. Each sidewall includes upper and lower sides 4a and 4b parallel to a longitudinal direction, and the lower side 4b is integrally connected to the bottom plate 3 so as to hold the sidewall perpendicular to the bottom plate. As shown in Fig. 2, the sidewalls 4A are arranged parallel to one another, and include long sidewalls and short sidewalls disposed alternately one another. The sidewalls 4B are arranged along a traverse direction at a right angle to the longitudinal direction of each sidewall 4A with predetermined intervals between them, and the central part of each sidewall 4B is integrally connected to an end portion of the elongated sidewall 4A. The sidewall 4C is arranged parallel to the sidewalls 4B.

[0015] The radiation plate 5 is made of a flat plate of aluminum and arranged parallel to the bottom plate 3 so as to provide a space between the bottom plate 3 and the radiation plate 5. One surface of the radiation plate 5 is fixed to the upper sides 4a of the sidewalls 4A, 4B and 4C at a plurality of points by spot welding. With this, the space between the bottom plate 3 and the radiation plate 5 is separated by the sidewalls into a plurality of waveguides communicated mutually with each other and disposed in predetermined pattern. Namely, radiation waveguides 7A parallel to one another are formed each defined by two adjacent sidewalls 4A, the bottom plate 3 and the radiation plate 5, and a feed waveguide 7B extending in a direction at a right angle with the radiation waveguides is formed between the sidewalls 4B and the sidewall 4C. The feed waveguide 7B is branched into adjacent two of the radiation waveguides 7A through each gap 18, thus forming a π branch. Cross slots 6 are formed at a part of the radiation plate 5 facing to each of the radiation waveguides 7A with predetermined intervals in the longitudinal direction of the waveguide. Further, inductive posts 10 are provided at positions on the bottom plate 3 facing to the feed waveguide 7B corresponding to the π branches. These posts 10 are made of aluminum integrally with the bottom plate 3. The radiation waveguide, the feed waveguide, the inductive post, the π branch and the cross slot described above are all well known. Since detailed description thereof is made in the document (4) mentioned above, it is requested to refer to the same.

[0016] The thickness of the bottom plate 3 is 1.5 mm, and the thickness of the radiation plate 5 is 0.3 mm. Each of the sidewalls 4A, 4B and 4C has a thickness of 1.0 mm, and a height, i.e., the distance between parallel sides 4a and 4b of 4.0 mm. Further, the distance between adjacent two sidewalls 4A, i.e., the width of the radiation waveguide 7A is 17 mm, and the distance between the sidewall 4B and the sidewall 4C, i.e., the width of the feed waveguide 7B is 34 mm.

[0017] The spot welding between the upper side 4a of each sidewall and the radiation plate 5 is made preferably by laser spot welding. The upper surface of the radiation plate 5 is irradiated with energy of 8 joules (Kw-msec) of YAG laser having the wavelength of 1.06 µm, thereby to spot weld the radiation plate to the upper side of the sidewall at intervals of 2.5 mm pitch. As shown in Fig. 4, the part irradiated with laser is melt so as to form a weld metal 8 thereby connecting fixedly the upper side 4a of the sidewall 4A to the radiation plate 5.

[0018] When an electromagnetic wave of 11.85 GHz is supplied to the antenna 1, the electromagnetic wave is transmitted outside through the feed waveguide 7B, the gaps 18, the radiation waveguides 7A and the slots 6.

[0019] Fig. 5 shows a typical section of a weld when welding is made by another spot welding method. In this spot welding, a dent 9 having a conical section is formed by punching in advance at an upper portion of the radiation plate 5 opposite to the spot-welding position and the spot-welding is applied to the portion of the dent 9. In this case, the applied power of the laser is saved, and it is possible to prevent excessive weld metal 8 from swelling on the upper surface of the radiation plate as shown in Fig. 4.

[0020] Next, another embodiment of the present invention will be described with reference to Fig. 6 and Fig. 7.

[0021] In this embodiment, an antenna 11 of a waveguide structure also includes a main body 12 and a radiation plate 15 made principally of aluminum like the embodiment shown in Fig. 1 and Fig. 2. The main body 12 is provided with a flat bottom plate 13 and a plurality of substantially rectangular elongated thin sidewalls 14A, 14B and 14C. The bottom plate 13 and the sidewalls 14A, 14B and 14C are made of aluminum in one block by casting, e.g., by a die casting method. Each sidewall includes upper and lower sides 14a and 14b parallel to each other in the longitudinal direction, and the lower side 14b is integrally connected to the bottom plate 13 in a block so as to hold the sidewall perpendicular to the bottom plate. The sidewalls 14A are arranged parallel to one another in the longitudinal direction with predetermined intervals, as shown in Fig. 7. The sidewalls 14B are arranged along direction at a right angle to the longitudinal direction of the sidewalls 14A with predetermined gaps 20 therebetween. The central part of each sidewall 14B is integrally fixed to the end portion of one sidewall 14A. The sidewall 14C is arranged parallel to the sidewalls 14B.

[0022] The radiation plate 15 is made of a flat aluminum plate and arranged parallel to the bottom plate 13, and one surface thereof is fixed to the upper sides 14a of the sidewalls 14A, 14B and 14C by spot welding. With this, a radiation waveguide 17A is defined by adjacent two sidewalls 14A, the bottom plate 13 and the radiation plate 15, and a feed waveguide 17B is formed between the sidewalls 14B and the sidewall 14C. The feed waveguide 17B is communicated with the radiation waveguides 17A through gaps 20, respectively. Cross slots 16 are formed at predetermined intervals along two lines in the longitudinal direction of the waveguide at a part of the radiation plate 15 facing to each radiation waveguide 17A.

[0023] The thickness of the bottom plate 13 is 1.5 mm, and the thickness of the radiation plate 15 is 0.3 mm. Each of the sidewalls 14A, 14B and 14C has a thickness of 1.0 mm, and a height, i.e., the distance between parallel sides 14a and 14b is 4.0 mm. Further, the distance between adjacent two sidewalls 14A, i.e., the width of the waveguide 17A, and the distance between the sidewall 14B and the sidewall 14C, i.e., the width of the waveguide 17B are both 17 mm.

[0024] The spot welding between the upper side 14a of each sidewall and the radiation plate 15 is made preferably by laser spot welding. The top surface of the radiation plate 15 is irradiated with a YAG laser beam having a wavelength of approximately 1.06 µm at energy of approximately 8 joules (Kw-msec), thereby to spot weld the radiation plate to the upper side of the sidewall at intervals of 2.5 mm pitch.

[0025] When an electromagnetic wave of 11.85 GHz is supplied to the antenna 11, the electromagnetic wave is transmitted outside through the feed waveguide 17B, the gaps 20, the radiation waveguides 17A and the slots 16.

Industrial Applicability

[0026] In an antenna of a waveguide structure and a method of manufacturing the same according to the present invention, since the sidewalls and the radiation plate are connected fixedly to each other by laser welding, it is possible to connect the main body and the radiation plate fixedly to each other with a small amount of weld metal. Accordingly, production steps are reduced and the sidewalls and the radiation plate can be made thinner as compared with a conventional method such as screw clamping, so that it is possible to make a lightweight antenna at a low price. Further, since the sidewalls are formed thin with less deformation in connection between the sidewalls and the radiation plate, the flatness of the internal surface of the waveguide is high and the transmission loss of the electromagnetic wave is small.

Claims

1. An antenna of a waveguide structure comprising:
   a flat thin metallic bottom plate;
   a flat thin metallic radiation plate arranged in parallel to said bottom plate and disposed at an interval from the bottom plate so as to provide a space between the bottom plate and the radiation plate; and
   a plurality of flat and thin metallic sidewalls arranged in said space and fixed to said bottom plate and said radiation plate so as to separate the space between said bottom plate and said radiation plate into a plurality of waveguides communicating with one another;
   wherein said radiation plate is welded to said plurality of sidewalls by a plurality of spot weldings at predetermined intervals.

2. An antenna of a waveguide structure according to Claim 1, wherein said bottom plate and said plurality of sidewalls are integrally made of aluminum.

3. An antenna of a waveguide structure according to Claim 2, wherein said radiation plate is made of aluminum.

4. An antenna of a waveguide structure according to Claim 1, wherein each of the predetermined intervals in the plurality of spot weldings between said radiation plate and said sidewall is 1/10 or less of a wavelength of an electromagnetic wave to be used in said antenna.

5. An antenna of a waveguide structure according to Claim 1, wherein each of said plurality of waveguides includes one feed waveguide and a plurality of radiation waveguides extending parallel to one another in a direction perpendicular to said feed waveguide.

6. An antenna of a waveguide structure according to Claim 5, wherein a plurality of slots are formed at a part of said radiation plate facing to each of said plurality of radiation waveguides.

7. An antenna of a waveguide structure comprising:
   a flat thin metallic bottom plate;
   a flat thin metallic radiation plate arranged in parallel to said bottom plate and disposed at an interval from the bottom plate so as to provide a space between the bottom plate and the radiation plate; and
   a plurality of flat and thin metallic sidewalls arranged in said space and fixed to said bottom plate and said radiation plate so as to separate the space between said bottom plate and said radiation plate into a plurality of waveguides communicating with one another;
   wherein said plurality of sidewalls are made in a single block of metallic material integrally with said bottom plate.

8. An antenna of a waveguide structure according to Claim 7, wherein said plurality of sidewalls are welded to said radiation plate by a plurality of spot weldings at predetermined intervals.

9. A method of manufacturing an antenna of a waveguide structure comprising:
   a flat thin metallic bottom plate;
   a flat thin metallic radiation plate arranged in parallel to said bottom plate and disposed at an interval from the bottom plate so as to provide a space between the bottom plate and the radiation plate; and
   a plurality of flat and thin metallic sidewalls arranged in said space and fixed to said bottom plate and said radiation plate so as to separate the space between said bottom plate and said radiation plate into a plurality of waveguides communicating with one another;
   said method comprising the step of welding each of said plurality of sidewalls to one surface of said radiation plate by laser welding.

10. A method according to Claim 9, further comprising the step of making said bottom plate and said plurality of sidewalls integrally of aluminum.

11. A method according to Claim 10, wherein said radiation plate is made of aluminum.

12. A method according to Claim 9, further comprising the step of making said bottom plate and said plurality of sidewalls integrally by casting.

13. A method according to Claim 9, further comprising the step of making said bottom plate and said plurality of sidewalls by die casting of aluminum.

14. A method according to Claim 9, further comprising the step of making said bottom plate and said plurality of sidewalls of aluminum by a lost wax method.

15. A method according to Claim 9, further comprising the step of making said bottom plate and said plurality of sidewalls of aluminum by a shell mold method.

16. A method according to Claim 9, wherein said plurality of sidewalls are welded to one surface of said radiation plate by a plurality of spot weldings at predetermined intervals.

17. A method according to Claim 16, wherein each of said predetermined intervals is 1/10 or less of a wavelength of an electromagnetic wave to be used in said antenna.

18. A method according to Claim 9, wherein the step of welding said plurality of sidewalls to one surface of said radiation plate by laser welding is performed by irradiation of a laser beam onto another surface of said radiation plate opposite to said one surface.

19. A method according to Claim 18, wherein said plurality of sidewalls are welded to one surface of said radiation plate by a plurality of spot weldings at predetermined intervals.

20. A method according to Claim 19, further comprising the step of forming a dent, before said plurality of sidewalls are spot-welded to the one surface of said radiation plate, at each of positions corresponding to said spot-welding positions on another surface of said radiation plate.

21. A method according to Claim 19, wherein said predetermined interval is 1/10 or less of the wavelength of the electromagnetic wave to be used in said antenna.

22. A method of manufacturing an antenna of a waveguide structure comprising:
   a flat thin metallic bottom plate;
   a flat thin metallic radiation plate arranged in parallel to said bottom plate and disposed at an interval from the bottom plate so as to provide a space between the bottom plate and the radiation plate; and
   a plurality of flat and thin metallic sidewalls arranged in said space and fixed to said bottom plate and said radiation plate so as to separate the space between said bottom plate and said radiation plate into a plurality of waveguides communicating with one another;
   said method comprising the step of forming said bottom plate and said plurality of sidewalls fixed to said bottom plate integrally in a single block of metallic material.

Drawing